Apparatus and method for forming extensions upon tubes



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APPARATUS AND METHOD FOR FORMING EXTENSIONS UPON TUBES 2 Sheets-Sheet Filed 001;. 2 1928 www I W MW YW Bw M/M M F f@ 7l f 5 wf L4 Y),

ATTORNEYS.

A. `T. HUNTER Dec.. 3, -1 929n APPARATUS AND METHOD FOR FORMING EXTENSIONS UPON TUBES Filed Oct. 2, 1928 2 Sheets-Sheet 2 INVENTOR.

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BY Mmmm, Kms@ +Mw A TTORNEYS.

atentecl Dec. 3, 1929 UNITED STATES PATENT OFFICE ARTHUR T. HUNTER, OIFy UNIVERSITY CITY, MISSOURI, .ASSIGNOR TO INTERNATIONAL COMBUSTION ENGINEERING CORPORATION, OF NEW YORK, N, Y., A CORPORATION OF DELAWE APPATUS ANI) METHOD FOR FORMING EXTENSIONS UPON TUBES Application filedl October 2, 1928. Serial No. 309,844.

tu which not merely protects the tube from injury from the radiant heat, but operates to afford a high rate of heat transfer from the face to the medium circulating in the tube. As such the present invention may be conlt sidered as an improvement upon my prior application, Serial No. 155,197, filed December 1G, 1926 for furnace water wall, wall element and method of making same, and upon the method thereof made the subject of divisional application, Serial No. 307,984,

filed September 24E, 1928, for method of form ing an extension upon a tube.

'llhe objects of the present invention include, in general, the improvement of method and apparatus for forming an extension or facing upon a tube; to secure a more uniform fusion and intimate uniting of the ex tension metal to the tube and therefore a more uniform product with improved heat au transfer; and to reduce the labor and therefore the expense entailed in the manufacture of the product, especially by the saving of labor in the making of cores and molding of sand. A further particular object is to reduce the tendency of the tube to curve or lwarp during the fusionprocess, this object being accomplished by effecting the heating not only of the front of the tube or side to which the extension is applied but also to the opposite side or back. 'Other and further objects and advantages of the invention will be explained in the hereinafter following description of an embodiment thereof or M will be understood by those conversant with the subject.

To the attainment of such objects and advantages the present invention comprises the novel method and apparatus, and the te novel features of operation, arrangement,

combination and construction herein illustrated or described.

In the drawings Fig. 1 is a transverse section of an illustrative form of a product of this invention, namely a boiler tube having an extension or facing integrally formed thereon.

Fig. 2 is a perspective view of a wall element or tube with the extension or facing applied sectionally along the length of the tube with gaps preventing warpage from expansion or growth.

Fig. 3 is a transverse vertical section view of an apparatus or mold embodying the present invention and suitable for carrying out the method hereof in the manufacture of a product such as shown in Figs. 1 and 2.

Fig. 4 is a skeleton perspective view of the apparatus of Fig. 3.

Fig. 5 is a combined elevation and section view, looking from the right, and taken substantiallyv on the broken line 5-5 of Fig. 3.

Fig. 6 is a View generally similar to Fig. 5 showing diagrammatically one method of manufacturing a sectional wall element as shown in Fig. 2, Fig. G showing the first stage of manufacture wherein alternate extensions are applied to the tube.

Fig. 7 is a view corresponding with Fig. 6, but showing the succeeding stage wherein the remaining extensions are applied to the tube.

Fig. 8 is a view similar to Fig. 3 showing a modified embodiment of the invention wherein the overflow metal is carried around to a recess at the Jfar or back side of the tube for heating at that side and equalizing the expansion effect at the other side.

, Fig. 9 is a view similar'to Figs. 6 and 'l showing a method of manufacture of the wall element-.of Fig. 2 wherein all of the extension sections are applied at the same time or in the same castingoperation.'

Fig. 10 is a perspective View of the product resulting from the use of the invention as illustrated in Figs. 8 and 9, and showin the surplus ,rnetal broken away from the-l ach side of the tube after setting. j j

` VIn Fig. 1 the tubular wall element is shown in cross section as consisting of the tube por ltd ltltl tion 11 containing the water passage or channel 12 and the exterior extension or facing 13 water being intended to include its vapor or steam, or other circulating fluid. The particular form of extension or facing 13 .may be described as comprising a body 1li and opposite Wings 15 rendering the facing substantially wider than the diameter of the tube, and the front face or exposed surface 16 extendin over the whole width and length of the bo y and wings.

According to this invention the tube portion 11 and the extension 13 consist preferably of different metals. The former may be a commercial seamless wrought steel boiler tube composed of mild steel low in carbon, while the extension consists preferably of cast iron, namely gray cast iron with high carbon content. The two portions of the finished product however are integral and the drawing indicates a theoretical division or line of union 17 between them. In the complete product the preformed tube 11 and the applied extension 13 are integrally united or fuse welded as will be herein described.

The purpose of the particular form of extension as shown in Fig. 1 is fully described in said application 155,197; it being especially constructed to increase the heat transferring action, for example transferring heatof radiation and convection from the interior of a furnace to the tiuid circulating in the tube. Effective heat transfer from the face 16 to the medium in the tube channel 12 requires the extension to be unitarily connected to the tube and the line of union 17 indicates a line of absolute contact and union, with molecules or crystals interlocked along the contiguous portions of the tube and extension.

For furnace purposes it is preferable not to have the extension applied continuously along the length of the tube and in Fig. 2 is shown a form of construction in which a series of short sections or extension 13, 13 are spaced along the tube with slight gaps 23 between them, both facilitating manufacture and allowing for expansion and growth without swelling or warping of the wall in practical use.

The tubular element thus described may be manufactured on an economical basis by the y apparatus and method hereinafter described.

The seamless steel tube 11 should first be thoroughly cleaned prior to the casting operations, for example by pickling and sand blasting until the surface to be united, corresponding with the union line 17, is bright and lclean. A portion of the length of the tube may then be inserted in a special mold such as is indicated in Figs. 3, 4 and 5. This mold may be split separately into a lower section 32 and above it a removable upper section or cope 33.

The casting space or cavity 34 corresponds with the shape of the facing extension 13 as seen in Fig. 1 and may bel formed by a suitable pattern positioned against the side of the tube during the molding of the sand. For conducting the molten iron into the casting space there are shown a seriesof sheet gates 35. These are not parallel with the tube as in my prior applications, but are turned at an angle, preferably a right angle, so that each gate delivers into the cavity an upright stream or sheet of molten metal. The tube standing preferably horizontal in the mold the sheet gates are preferably vertical and each of them is relatively thin and is tapered at its delivery so as to give the effect of a nozzle in order to inject the molten metal with substantial velocity into the casting space. The several sheet gates may be substantially parallel as shown and are all supplied with molten metal from a common receiving spout 3G. The lnetal will have substantial heat and will enter the cavity forcibly and will effectively flow through all parts of the cavity and in contact with all exposed parts of the preformed tube ll.

As in the prior applications it is herein intended to fiow the metal through the mold or a substantial period of time and a sheet riser 38 is shown conducting the overflow metal upwardly from the cavity to an overflow gutter 39. The gutter being of less height than the inlet spout, a continuous llow will be maintained b gravity. The riser 38 is preferably inthe filirm of a single flat exit from the mold, extending substantially parallel to the axis of the tube 11. The described arrangement of sheet gates 35 and riser 38 is found to give an effective heating of the tube to the softening or fuse welding point.

In Figs. 3 5 the mold may be considered as packed with green sand 40 but the ends of the molding cavity preferably closed with packed sand cores 43, their outline beingl indicated in dotted lines in Fig.

Preferably the performed wrought steel tube is preheated to a fairly high degree, for example between S00o and 90()O F., to assist the softening of the metal and preparing it for the fuse welding operation by which the facing extensions are applied integrally to the tube. For such purposes a burner or torch 45 is indicated and this may be used to drive the flames through the tube as in said prior application.

In carrying out the method it will be understood that the molten east iron progressively elevates the temperature of the exposed portion of the steel tube. The forcible intlowof molten metal into the casting recess produces etfective distribution ot the heat to all exposed parts of the tube. This` roduces a substantially uniform heating e tfect in connection with the torch or other internal heating means, and the inflow and overtiow of hot molten metal is continued until the steel is raised to welding temperature,

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'Wausau for example between 12500 and i300@ F. at which it will be understood the metal is sot tened but not melted. ln other words the Inaterialofthe tube is put in condition for molecular union withthe cast extension, but without. permitting 'interflow as between the two metals or any such displacement of deformation of the metal of the tube as to wealren the latter or render it unsafe for high pressure boiler purposes.

Preferably the operation is carried out by pouring from a. ladle an excess amount of molten iron, for example three or four times the weight of the casting to be produced so as to aflord a prolonged tube heating opera` tion. llFhe pouringv is preferably first eifected at a rapid speed until the cavity is full, but then slowed down to avoid erosion of the steel and to prolong the heating action; the total time of pouring and over-dow being for errample in the neighborhood of one minute more or less.

Figs. 6 and 7 indicate a methodof manufacture wherein alternate extensions are formed on the tube and allowed to set, following which, perhaps on the succeeding day, the remaining extensions are applied. An elongated tlaslr 47 is shown containing sand molded as in Figs. 3-5 for the production of alternate extensions, the intermediate spaces being occupied by green sand dit, this hown ever being separated by the baked end cores t3 from the respective casting spaces. lt will be understood that according to Fig. 6 the several extensions are cast in a single operation, meaning generally in the same period or day. The molten metal may be poured successively into the several mold recesses from a single ladle, or from a nurnber of ladles, or the mold may be formed with channels leading from a common pouring spout or inlet to the several recesses as shown in said prior applications.

After the alternate extensions are formed as in Fig. and have been allowed to set the forming of the remaining or intermediate extensions may be eected as in Fig. 7 where the operations are substantially identical, the extension being defined by the molded green sand and by the end cores as before. When.

the second casting operation is completed and the cast metal has set, the end cores will be removed from the spaces between the eX- tensions, and. after cleaning and removal of surplus metal the tubular element is in readiness for practical use.

'lhe method indicated in Figs. 8, 9 and l() is different in certain respects. In the first place the successive mold cavities are defined not by molded green sand, but by hard or baked cores. The exterior flask 5l may contain a lining of green sand, this giving support to a system of baked cores 53 of the desired shape and assembled in the mold ben fore the insertion of the tube ll therein.

'.lhis system permits greater production as certain worlrmen can manufacture the necessary cores while others are applying the cores and forming the molds. rlhe cavity or recess 51tin which the extension is molded is defined by the halted core 53 and the surface of the tube ll and a flat baked core 55 at each end of the cavity.

'lhe molding cavity 5t and the sheet gates 55 leading to it and the inlet or spout 57 may be substantially as in Figs. 3-5. llnstead however of a sheet riser as in Figs. 3 5 there is shown a sheet channel 58 which does not deliver from the mold but delivers into a baclr cavity or recess 59 at the opposite side of the tube 1l from the molding space 5t. By this arrangement the excess or overdow 'metal from the molding space is carried over into the back recess and operates to heat up the baclr side of the tube so as to equalize or neutralize the expansion and resulting warpage which the heating at the other side tends to produce. Preferably the back recess 59 is commensurate in volume with the front recess 5ll so that the heatingl effects are substan tially equal. 'Ehe molten metal will have cooled sutliciently before contact with the back side of the tube to obviate adherence thereto and it will be found that the back castin 60 is readily detached and discarded, as indicated in Fig. l0, leaving the tube with integral extension in the desired form as shown in Figs. l, 2 and l0.

Since preferably more than twice the volume of metal is employed as is necessary to till the molding recess 5d., and sometimes four or more times the volume, it is necessary toprovide an outlet from the back recess 59. For this purpose a riser 6l is shown leading u wardly from the baclr recess. Therelation ol: the channel 58 and riser 6l are not such as to cause a tendency toezrtreine oruniforln heating of the metal of the tube ll, since the set metal or block formed in the rear back cavity is to be detached and discarded. At its upper end the riser 61 may deliver into a gutter 62 which carries the excess metal olf to any suitable receiving point.

Each two of the main baked cores 53 conline an end core 55 between them, and this may suffice to hold the latter securely, or green sand may be rammed in for additional support, or the main cores may have shoulders or recesses receiving the end cores.

A salient difference between the method of Figs. 6 and 7 on the one hand and Figs. 8 and 9 on the other hand is as follows. ln the first stage shown in Fig. 6 the baked end cores 43 are backed up by green sand and therefore able to resist the casting pressure; whilein Fig. 7 the end cores are backed up by the alternate extensions already cast. In Figs. 8 and 9 however the end cores 55, while held between the main cores 53, are not backed up in a direction lengthwise of the tube and are Btl lll)

therefore'subjected not only to the high temperature of the molten metal, but to the face pressure thereof, which, in the case of a mere baked sand end core would tend to break or 5 displace the core and impair the product. I therefore propose in carrying out the method of Figs. 8 and 9 to employ end cores 55. of high physical strength. Such a core may be made of sand or similar material coated upon 10 an internal plate of metal such as iron to give the strength and refractory properties. This however is not entirely satisfactory in all cases, especially where the core is relatively thin as it is apt to present difficulties in removing it from the thin space 23 bet-Ween successive extensions, especially if any possible fusing of the iron plate occurs. I therefore propose in such cases to employ an end core 'of silicon carbide or other similar rigid material having the strength to resist the pressure andsthe refractory property to resist the temperature, such core, if desired, being coated with a layer of sand pasted on each side to facilitate its subsequent removal from the finished product.

There have thusbeen described an apparatus and method for forming an extension upon a tube embodying the principles and attaining the objects oftj the present in- 80 vention. Since many matters of method, operation, combination, arrangement and structure may be variously modified without departing from the principles of the invention it is not intended to limit the invention to such matters except to the extent set forth in the appended claims.

What is claimed is: f

1. The method of forming upon one side of a reformed steel tube an integral heat Arig) absor ing extension of ferrous metal comprising supporting the tube in position in a .mold with its side that is to receive the extension` exposed in a casting space of the shape of the extension to be formed, flowing molten (i5-ferrous metal into the casting space in relatively thin wide sheets disposedat an angle to the length of the tube and thence throughy and from the space in excess quantity, continuing such fiowing for a sufficiently long period to raise the metal of the tube to a softening temperature at its exposed circumference, but stopping the flowing before erosion, and then permitting the combined tube and extension to cool and set.

2. The method' as in claim 1 and wherein the preformed tube is maintained substan tially horizontal during operation, and the moltenextension metal is flowed thereto in upright sheets and delivered with nozzle'effect ee to produce velocity and intensive heating of l the tube.

3. Apparatus for forming an extension on a tube com rising a mold containing molding materia disposed to define a space of the e5 shape ofthe extension adjacent the tube, and

defining sheet gates or passages deliverin into the molding space at substantiall right angles to the length of the tube, and efinm an exit passage for surplus metal flowe through the space.

4. Apparatus forlforming an extension on a tube comprising a mold containing molding material disposed to define a space of the shape of the extension and defining one or more sheet gates or passages of tapered form and delivering into the molding space at substantially right angles to the len rth of the tube, and defining an exit passage fPor surplus met-al fiowed through the space.

5. Apparatus as in claim 3 and wherein the molding material defines, with the tube, the cross sectional shape of the extension, and with separate hard end cores defining the length of the extension.

6. Apparatus as in claim 3 and wherein the molding material defines, with the tube, the cross sectional shape of the extension, and with separate hard end cores defining the length of the extension, said end cores comprising rigid material as silicon carbide giving high strength and refractory properties.

7. The method of forming upon one side of a preformed wrought steel tube an integral heat absorbing extension of ferrous metal comprising supporting the tube in position in a mold with its side that is to recelve the exu tension exposed in a casting space of the-shape of the extension to be formed, and its opposite side exposed in a heating cavity, {iowing molten ferrous metal into the casting space and through and from the space in excess quantity, continuing such flowing for a sufficiently long period to raise the metal of the tube to a softening temperature at its exposed circumference, but stopping the flowing before erosion, flowing the surplus metal from the casting space around the tube and into the tube heatin cavity to raise the opposite side of the tube to a hot temperature below the softening point to neutralize substantially the tendency towarping from the longitudinal expansion at the first side, and then permitting the united tube and extension to cool and set, and removing the surplus metal solidified in the heating cavity.

8. Apparatus for forming an extension on a tube comprising a mold containing molding material disposed to define a space of the shape of the extension and defining a passage delivering into the molding space,rand a passage from `the space for surplus metal flowed through the heating space, anda space at the opposite side of the tube into which such passage delivers.

In testimony whereof, this specification has been duly signed by:

ARTHUR T. HUNTER. 

